Dynamic Furniture Replacement in Three.js

To implement dynamic replacement of placeholder objects with properly positioned glTF furniture models, you'll need to use the GLTFLoader from Three.js along with some strategic scene management. Here's a comprehensive approach:

1. Loading the Room and Furniture Models

First, use the GLTFLoader to load your room and furniture models:

JAVASCRIPTCopied
import { GLTFLoader } from 'three/examples/jsm/loaders/GLTFLoader.js';

const loader = new GLTFLoader();

// Load the room
loader.load('path/to/room.gltf', (roomGltf) => {
  const roomScene = roomGltf.scene;
  scene.add(roomScene);
  
  // After room is loaded, identify placeholders and replace them
  replacePlaceholders(roomScene);
});

// Function to load furniture models
function loadFurnitureModel(modelPath) {
  return new Promise((resolve) => {
    loader.load(modelPath, (gltf) => {
      resolve(gltf.scene);
    });
  });
}

2. Identifying Placeholders

You need a consistent way to identify which objects in the room are placeholders. Some strategies:

• Use naming conventions (e.g., "placeholder_chair", "placeholder_table")
• Add custom user data to placeholder objects in your modeling software
• Use specific mesh properties or materials

JAVASCRIPTCopied
async function replacePlaceholders(roomScene) {
  // Find all placeholder objects
  const placeholders = [];
  roomScene.traverse((object) => {
    // Check if object name starts with "placeholder_"
    if (object.name && object.name.startsWith('placeholder_')) {
      placeholders.push(object);
    }
  });
  
  // Replace each placeholder
  for (const placeholder of placeholders) {
    await replacePlaceholder(placeholder);
  }
}

3. Replacing Placeholders with Furniture

When replacing placeholders, you need to:

• Determine which furniture model to use
• Preserve the position, rotation, and scale of the placeholder
• Ensure proper alignment

JAVASCRIPTCopied
async function replacePlaceholder(placeholder) {
  // Extract furniture type from placeholder name (e.g., "placeholder_chair" -> "chair")
  const furnitureType = placeholder.name.split('_')[1];
  
  // Load the corresponding furniture model
  const furnitureModel = await loadFurnitureModel(`models/${furnitureType}.gltf`);
  
  // Copy position, rotation, and scale from placeholder
  furnitureModel.position.copy(placeholder.position);
  furnitureModel.rotation.copy(placeholder.rotation);
  
  // For scale, you might need to adjust based on the model
  // Option 1: Direct copy if models are properly scaled
  furnitureModel.scale.copy(placeholder.scale);
  
  // Option 2: Adjust scale based on bounding box comparison
  adjustModelScale(furnitureModel, placeholder);
  
  // Add the furniture to the scene
  placeholder.parent.add(furnitureModel);
  
  // Remove the placeholder
  placeholder.parent.remove(placeholder);
}

4. Ensuring Proper Positioning and Scaling

To ensure furniture is properly positioned (e.g., on the floor, not upside down):

JAVASCRIPTCopied
function adjustModelScale(model, placeholder) {
  // Calculate bounding boxes
  const placeholderBox = new THREE.Box3().setFromObject(placeholder);
  const modelBox = new THREE.Box3().setFromObject(model);
  
  // Get dimensions
  const placeholderSize = placeholderBox.getSize(new THREE.Vector3());
  const modelSize = modelBox.getSize(new THREE.Vector3());
  
  // Calculate scale factors
  const scaleX = placeholderSize.x / modelSize.x;
  const scaleY = placeholderSize.y / modelSize.y;
  const scaleZ = placeholderSize.z / modelSize.z;
  
  // Apply scale
  model.scale.set(scaleX, scaleY, scaleZ);
  
  // Adjust position to align with floor if needed
  // This assumes Y is up in your coordinate system
  const placeholderBottom = placeholderBox.min.y;
  const modelBottom = modelBox.min.y * scaleY;
  const yOffset = placeholderBottom - modelBottom;
  model.position.y += yOffset;
}

5. Additional Considerations

Handling Different Orientations

If your furniture models might have different default orientations:

JAVASCRIPTCopied
function correctOrientation(model, expectedUp = new THREE.Vector3(0, 1, 0)) {
  // Determine model's current "up" direction
  // This is a simplified example - you might need more complex logic
  
  // Rotate to match expected orientation
  model.rotateX(Math.PI / 2); // Example rotation adjustment
}

Handling Model-Specific Adjustments

Create a configuration for each furniture type:

JAVASCRIPTCopied
const furnitureConfig = {
  chair: {
    rotationAdjust: new THREE.Euler(0, Math.PI, 0),
    scaleAdjust: 0.9, // Slight reduction in size
    heightOffset: 0.05 // Lift slightly off the ground
  },
  table: {
    // Table-specific adjustments
  }
};

// Apply in your replacement function
function applyModelSpecificAdjustments(model, furnitureType) {
  const config = furnitureConfig[furnitureType];
  if (config) {
    if (config.rotationAdjust) model.rotation.copy(config.rotationAdjust);
    if (config.scaleAdjust) model.scale.multiplyScalar(config.scaleAdjust);
    if (config.heightOffset) model.position.y += config.heightOffset;
  }
}

This approach gives you a flexible system for dynamically replacing placeholder objects with properly positioned furniture models in your Three.js scene.